Piston ring



Oct. 23, 1934. G. H. ROBERTS 1,978,061

PISTQN RING Filed 001;; 31, 1951 2 Sheets-Sheet 1 INVENTOR 'fieorge H.Roberts BY Patented Oct. 23, 1934 I J 'UNITED STATESTPAITEN'T F 1 I 1.18.061 t I George 11]., assignor to American Trust Company,

Davenport, Iowa, a

corporation of Iowa, trustee Application October 31, 1931, Serial No.572,280

' 2 olsimsjwi sea-32) This invention, which is a continuation in part ofmy co-pending application Serial No. 212,560, filed August 12, 1927,relates to piston and packing ring assemblies for the'main and valvecylin- 5 ders of steam engines. t In steam engine practice, andparticularly in those engines, such as locomotives, using piston valvesto control the flow of steam to the main cylinder, cylinder wallpressures between. first, 1

sure. The result is that these greater pressures cause unnecessary wearon both the cylinder or valve cage walls and the packing-rings. These"of the packing rings and the pressure of the steam behind the ring.Cylinder wall pressures are,

therefore, in no way controlled to obtain'a minimum cylinder wallfriction while maintaining an adequate but not excessive seal. P

It is, therefore, one of the objects. of the present invention toprovide a piston and ring assembly for steam engines in which thepressure between the packing ring and surrounding cylinder wall or valvecage is of such magnitude as to maintain an adequate seal for steampressure existing within the cylinders without excessive frictionalengagement with the cylinder wall.

Another object is to provide a steam engine pistonand ring assembly inwhich the expansion of the ring, and, therefore, the magnitude "offrictional contact, is controlled at all times inorder to avoidunnecessary high cylinder wall pressures, and thereby to increase thelife and performance of the assembly as compared with conventionalconstructions. 4 40 Another object is to provide a steam engine pistonand ring assembly which, during operation in an engine cylinder,adequately seals the steam pressures with a minimum of cylinder wallfric-- tion. A further object is to provide a steam engine piston andring assembly of such construction that steam pressures act radially andaxially against" the ring, and in which the radial expansion of the ringis resisted by frictional engagement with an inclined portion of thepiston body.

A still further object is to provide a steam engine piston or pistonvalve and packing ring assembly in which the increased expansivetendency of the packing ring is modified in order to avoid excessivecylinder wall pressure.

the piston valve packing rings and valve cage, and second, the maincylinder and piston packing ring, are created which are greater inmagnitude I than necessary to seal the existing steam presi engine, suchas a locomotive.

scribed in detail contemplates the use .of a packing ring having aninclined surface remotefrom 5 the side against which the steam pressuresact,

which cooperates with a correspondingly inclined surface of the pistonbody. The ring isassems ble'd in the piston with substantial axial andradial clearances with respect to the piston body 7 so that the existingsteam pressure may act both radlally'and axiallyagainst the ring andexpand it against the frictional resistance created by the contactbetween the inclined surfaces of the ring and piston. The ring, becauseof the material axial clearance, has a tendency to float and properlyalign itself.

The invention may beincorporated in the main piston and in the pistonvalve as shown in the drawings of which Figure 1 is a section showingone arrangement of the main pistonand cylinder and the piston valvewhich controls the supply of steam to and the discharge of steam fromthe main cylinder.

Figure 2 is an enlarged fragmentary section taken through the mainpiston assembly and showing the piston and the packing ring constructionin detail.

Figure 3 is a fragmentary'enlarged section of a piston valve showing thecooperation between the packing ring and the piston valve proper, and

Figure 4 is a fragmentary section similar to Figure 3 showing onemodification of the packing ring Referring. to the accompanying drawingsin which likenumerals refer to like parts throughout the several views,I have shown in Figure 1 the relative positions of the steam chest, maincyl-' inder,'piston valve and the main piston of a steam As shown inthis view, the assembly comprises a main cylinder 1 having a piston 2reciprocably mounted therein, the piston-2 being provided with asuitable drive rod 3., Steam is admitted into the'ends of the maincylinder 1 at opposite sides of the piston through passageways 4 thatlead from Opposite ends of the steam chest 5. The

steam chest is of a conventional type and has a central inlet 6 andcylindrical valve seats or cages 7, provided with ports 8 thatcommunicate with tion 12 of the spiders.

-9 which permits the the passageways 4. The ports 8 are alternatelyopened and closed by a conventional piston valve flow of steam intooneend of the main cylinder 1 during the exhaust of steam from the otherend of the main cylinder.

Referring particularly to Figures .1 and 3, the piston valve 9 ismounted on a valve rod 10 by means of spiders 11, keyed to the rod 10 atopposite ends.- Each spider is, formed with a cylindrical portion 12coaxial outwardly extending radial lindrical body of the valve thespiders 11 as shown and'has 'shoul-l ders 14 at its ends which havecentering-as well as thrust engagement with flange 13. The cy-Surrounding the cylindrical portions 12 of each spider, and conflnedbetween ring 15 which forms a guide forthat end of the valve in theseator cage 7. The annular bull ring, which is continuous and substantiallynonexpansive, is held against rotation "on its spider 11 in any suitablemanner. I

-The piston valve is provided with two expansible rings. at each end toprovide sealsbetween the valve and valve cages. the outermost ringv 16 uat each end being the exhaust ring and the innermost ring 17 at each endbeing the steam ring.

It is obvious that the purpose of the exhaust rings 16 is to prevent theleakage of steam between t g the exhaust sides of each valve cage 7 andthe. steam passageways, and that the purpose of the steam rings 17 is toprevent leakage of high pressure steam between the steam chestand theport '8 that is closed by the piston valve.

The present invention, as regards the piston valve described, extendsprimarily to the steam rings 17. The exhaust rings 16. as here shown,

7 are of a conventional type and are mounted between the spider andflanges l3 and the bull ring 15 in recesses formed at theintersections'of the outer lateral and circumferential faces of the bullring and need not be further described.

The steam rings 17 are likewise mounted between'the ends of the body ofthe piston valve and,

the bull rings 15 in suitable recesses 18 formed at the intersections ofthe inner lateral and circumferential faces of the bull rings 15. Eachrecess 18 includes a circumferential face 19 and a face 20 that isinclined outwardly toward the opposite end of thespiston valve. It is tobe noted, however, that the faces of the shoulders 14 of the valve bodyare spaced axially inwardly fromthe outer marginal edges of the inclinedfaces 20 to provide spaces the steam rings 17.

Each steam ring 17 is of the split type, having an inclined face 21 thatsubstantially corresponds tothe face 20 of the bull ring, the oppositeside, a narrow outer circumferential face 23 and a widerinner'circumferential face 24. .The ring 17 is mounted in its recessduring the assembly of the piston valve parts described and materialaxial and radial clearances are mainfor the reception of tained betweenthe ring and the cooperating valve parts so that the ring may have sidecontact with either the inclined face 20 of the bull ring or the radialface'25 of the shoulders 14 of the piston valve body depending, ofcourse, upon the action of the steam pressure and the direction of move-The ring 17. therefore,

ment of the piston valve.

has a floating action within its recess. 7 H Steam pressures within thesteam chest are actically constant. The steam acts both axially with therod and an,

is clamped between the spider flange 13 and end of the valve body, is"an annular bull,

a radial face 22 at.

aswellasradiallyagainsttheringbyreasonof the axial and radial clearancesthat are provided, withtheresultthattheradialpressuresamistin expandingthe ring. The ring 17, however, is provided with some snap in order thatit will ciri cumferentially engage the wall of the surrounding cage. Theoutward expansion of the ring, caused by the initial snap and the radialcomponents of steam pressure, however, is resisted by the frictionforces set up by the inclined faces 5 20 and 21 of the bull ring 15 andpacking ring 17, respectively, which are in contact. It may be said,therefore, that the expansion forces created by the pressure of thesteam in'the steam chest are partially neutralized or modified by there- 9 sistance to expansion created by the forces'set up faces.

The m nitude of the pressure exerted by the ring against the wall of thesurrounding cage is dependent upon three factors, namely, one, 9 thesnap of the ring, two, therelative area of the faces 21, 22 and 24 ofthe packing ring, and, three, the angle of inclination of the ring face21. It is obvious that by increasing or decreasing the angle ofinclination of the coacting faces 20 and 10( 21 the magnitude of thewall pressure will be decreased or increased accordingly. Furthermore,it is obvious that the magnitude of the wall pressure may also be variedto some extent by changing the areas of the axial and 106 radial ringfaces 24 and 22, respectively. Since the pressure of the steam in thechest is relatively high and constant during the stroke of the piston,it is desirable to use angles of inclination that are relatively high.In the drawings 110 I have shown the ring 17 as having inclinationangles of aproximately 45 degrees. These angles, however, may be varieddependent, of course, upon existing conditions.

In Figure 4 I have shown the steam ring 17.

In Figure 4 the ring 17b is of the modified L havins a portion 27extending beyond the radial face 28 of the valve body. The inner face ofthis portion 27 is inclined toward the radial face 22 of the packingring and provides with the-end of the valve body a circumferentialpocket 29 for receiving the steam and diresting it between the ring andpiston. valve.

. In each of the constructions shown in Figures 3 and 4, the steam ringis mounted within its recesswith material axial and radial clearanceswhich permit the proper action of the pressure .ly neutralized by thecontacting inclined faces 20 and21.

Furthermore, the steam rings described are boxed in during the assemblyof the piston valve parts by the bull ring 15 and end of the valve bodyso that 'in the case of breakage the broken parts of the ring will beheld from entering or interfering with the valve cage ports 8.

It will be seen that the circumferential sealing face 23 is relativelynarrow and that the linner circumferential face against which thepressure of the steam acts, is considerably wider. However, the width ofthe outer circumferential face 23 canbe increased in the manner shown inFigure 4.

One of the advantageous features that results from the use of the ringof the present invention :is that the ring has a substantial floatingacion within its'surrounding recess, which results a modified type of uswith thesurrounding wall. and thereby prevents wear- "ing oi! oi thecorners oi-the packingiringwhich might eventually permit steam t'oleakpast the Another advantage is the was or the portions of thecages-brldsinglthej ports 8 is materially reduced, thereby eliminatingdishing out of these'bridging portions. In the use oi conventional ringsthe pressureof the ring on proper alignment of the ring in the cylinder.

the cylinder wall is relatively great, and causes, because of thesmaller area of the cage in the plane of the ported, a greatenwear, onthese portions than on the other portions of the cage. presentinvention, the

By using the rings or the degree of wear of these" bridging-portions fora given period of time is' materially reduced, due to the lesserpressure on the cylinder'wall.

7 As previously stated, the packing'ring oi the,

present invention alsoextends to the main piston assembly. In Figures 1'and 2, Ihave shcwnthe invention incorporated in the main piston 2. Thepiston 2 embodies a disc carried by the piston rod 3 to which an annularmember =31 is rigidly secured. This member carries two packing rings 32mounted inopposed relation sincethe high pressure steam acts alternatelyagainst opposite sides of the piston. These rings function to seal boththe-exhaust and live steam pressure.

Packing ring grooves are arranged at'each side oithe central portion 33of the member 31. and

it is to 'be noted that the portions of the member 31 outwardly of thegrooves Stare of lesser diameter thanthe central portion-32. f

The outer and inner side walls 35 and 36,

respectively, of each groove are inclined from.

their periphery toward the side walls or the other groove at asubstantial angle as shown in Figure 2. Each packing ring 32 is oi thesplit type and has an inner lateral face 37 inclined to substantiallythesame degree as the groove wall 38, and an outer lateral tace that hasa relatively narrow face portion .38 inclined to substantially the sameangle as the groove sidewall 35.- and a substantially radial raceportion 89 extending radially outwardly from the inclined portion 38. Insome cases. the inclined portion 38 may be omitted. leaving onlyoneinclined face and thus ph -renting aring or trapezoidal Eachring flismountedinits admins mas terial radial and axial: clearances as shownin Figure 2 to permit the pressure oi the steam to act both radially andaxially against the packing ring. It is to be noted'that the groovewalls 35 and the radial portions 39 of the ring diverge towardtheperiphery and-provide a substantial pocket 40 therebetween. The outerends of the member 31 are of lesser diameter than the central portion33, and .thereby, because of their clearance with the cylinder wail,permit a flow of steam through the pocket. Y40 and clearance spacebetween the ring and groove walls 35, and into the space between thering and bottom'ot the groove. The rings 32 are provided with an initialsnap suiiicient to cause the ring to engage with the cylinder wall, andthe angles ot "inclination oi the sides 0! the ring oi expandingpressure produced by the initial snap oi the ring and the radialcomponents of steam pressure are resisted and materially modifled by thefrictional forces created between the rings and inner walls 35 oi thegrooves, so that that the sealing wall pressure for the high steam 'ent.invention,-however, the controlling of the and corresponding sidesoi"the groove walls are such that, duringthe operation oi the piston, theresultant radial component the cylinder wall pressures will provide anadequate seaL-but will not create excessive frictional forces which tendto wear boththe outer faces 0! I It is to-be notedthat the two rings 32are of the same construction, but are mounted in oppoa sition to eachother, so that when one of the rings is operating on its power stroke toseal the high steam pressures, the opposite ring is operating in .thesamemanner with diilerent forces to main-v "tain a seal.Consequently,'i'or the major part or each cycle both rings are undervariable pressures,

and the pocket 40, together with the clearance space between the ringand outer groove wall, is utilized to control'the-expansion oi .thering.

The exhaust steam pressures are considerablyless than thedrivingpressures and it is obvious pressures is higher than necessary for theexhaust .steam pressures. By utilizing the piston and .packing ringassembly 01' the present invention, the cylinder wall pressureduring theexhaust. 7 stroke or each packing ring is materially reduced,

but suflicient to maintain an adequate seal with a minimum of wallfriction. As a result the wear. of both the cylinder wall and'thepacking rings is of materially lesser magnitude than when conventionalrings are employed, in which case the m cylinder wall pressures createdby therings and steam pressures are excessive during the exhaust andpower movement.

when each ring is operating during its exhaust stroke, a pressure ismaintained in the pocket 40 and the space in back of the-ring whichtends to keep the ring engaged with the cylinder wall and with the innergroove wall 36, ready ior the power stroke. "The seat provided betweenthe rings 32, and inner walls 35o! the ring grooves may be arranged atany desired angle of inclination and .may. be'oi any suitable width,depending somewhat uponthe'existing conditions.

When wear takes place in conventional rings and groove walls, excessivesteam pressures are set up backer the rings, therebycausingexcesresultin greater wear'on the walls. ring faces and cylinders and lesslubrication. In the prespressure of the ring against the cylinder walland the floating action or the ring resultin less pressure on thecylinder wall and consequently less wear while maintaining an adequateseal between the piston and cylinder, even after the groove wallshavebecome worn. 3

Due to the material axial clearance, the rings of the present-inventionfor both the piston and piston valve are preie'rabLv mounted within thegrooves with their ends in abutting relation to 140 7 providea-substantlally continuous circumferential seal with the cylinderwallslthus preventing substantial leakage or steam between the ends ofthe ring.- l

-It is thus seen that the present invention is 1 applicable toboththemain piston and piston valve assemblies, and that in each case theaction or the ring is Practically the same, that is, the expansivetendencies of the ring due to steam 1 sive pressures against thecylinder walls which ringsand V particulariorm of apparatus shown anddescribed,-andthe particular procedure set forth,

, are presented for purposes of explanation and ppended claims.

illustration :and that various modifications of said apparatusandprocedure can be made without departingitrom my invention as WhatIclaim-isz I 1. Qpiston andpackingring assembly fora steamenginecylinder, comprising a piston body, having acylindrical portionand spaced radial flanges extending radially outwardly from saidcylindrical portion, an endless, relatively inexpansible bull-ringsurrounding saidcylindrical,

portions and disposed between said flanges, said. bull ringdefining withone of 'said'flanges a circumierential packing ring groove, the face ofsaid flange adjacent said bull ring forming one side wall of said groovean-d'said bullring forming the' other side .walland the bottom of saidgroove, said last rnentioneddside wall being inclinedin the directionotactionof the steam in the cylinder, and from its periphery toward theaxis of said groove, and an imperforate steam packing ring havingitsside faces inclined with respect to each other, the side face of thering adjacent said in clined groove side wall being inclined tosubstantiallythe: same angle as said inclined groove side enga ementbetween axial defined in the each of said bull rings forming with theadjacent abutment flange a steam ring groove and with steam rings havingtheir respect to each other, the side faces v sidewalls. .wall, saidpacking ring being mountedfin I .7

said groove with material axial and radial clearances, said axialclearance being suflicient when said packing ring is in engagement withthe cylinder, and said inclined groove side wall to prevent a saidpacking ring and the other groove side wall.

2. A piston valve and ring assembly for steam engines, comprising acylindrical body portion having radial abutment flanges at its ends, enda members having axial flanges abutting against said abutment ,flangesandradial flanges spaced from said abutment flanges, bull rings mountedon said Y flanges and positioned between the radial flanges of said bodyportion and end members the adjacent end member flange an exhaust ringgroove, the faces of said bull rings forming the sidewalls of said steamring grooves being inclined irom their peripheries toward the axis ofthe assembly and in the direction of action of steam, exhaust ringsmounted in said exhaust ring grooves and imperforate split steam ringsmounted in said steam ring grooves, each of said side faces inclinedwith of said rings adjacent said inclined groove side walls being in-.clined to-substantially the same angle as the inclinedgroove side wallof its adjacent bull ring and being mounted in its groove with material5 axial and radial clearances, the axial clearances of said rings beingsuflicient when the same are .in engagement with the cylinder and withthe inclined groove side -:walls to prevent engagement between the steamrings and the opposite groove 1m GEORGE H. ROBERTS.

